Did you not play the video?
Destructive in the sense of adding filters, as in adjustments once made, then wanting to change each filter. The basic one filter edit is easy, but after applying many filters then wanting to alter one filter is just impossible.
Apply filter 1, apply filter 2.
To get back to filter 1, you have to undo filter 2.
You have to undo filter 1 to change the settings.

@Paul2 I am using a Samsung Note 5, which about 3 years old if I remember correctly and my wife is using a Samsung Note 8 which only about a year and a half old. Neither of which could hear the audio except hers, but only when she put on headphones.

@Hudson555x I was getting the same issue when I uploaded my source footage to YouTube, so it is not because of Audacity.

Once I get the final video uploaded to YouTube I will post it here, just to let you guys see how it is compared to that original video. The fix takes a little extra editing but seemed to sound pretty decent, probably not perfect but we will make do until we can afford to upgrade to a better setup.

I still think the explanation of stereo phase cancellation during mono mixdown is the culprit. Why does it seem like this is being dismissed?

Not impossible but highly unlikely in this case.
My rationale as follows:
I take an existing clip that I know works on the Android phone, import it into shotcut and mute it’s audio.
Then add a new sound track (stereo) for the exact duration of the video clip.
Export it as h264 baseline 1280X720 with AAC audio (as per the specs of the original playable clip) and bang…no audio on the Android phone.

Looking at the details, the only difference are the durations as I described in my earlier post.
I know that the audio and video tracks on my edit are exactly the same length.

Well, well, well, I’ll be …
I re-read the last post from @shotcut and @djcorus and two things stood out.
Phase cancelation and “it worked with headphones”.

Went back to the original clip from @djcorus played it on my Android using headphones and what do you know…there is audio.
What the …?

Why when the built in speaker is used there is no sound but when there are headphones there is?
So decided to try a little experiment, extracted the audio from the original clip posted by @djcorus and imported it into Audacity (sorry @Hudson555x I know how much you like Audacity ) then did a mix down to mono, and what do we get? …

Now just today we re-shot the footage we needed. This time we used the same mic and camera but a friend of mine borrowed me a preamp/mixer. This time the source footage uploaded to YouTube played just fine on the phone. Could the mic not going through a preamp cause the channel to be out of phase? I guess even though we’ve figured out the fix, I’m still trying to figure out why it happened in the first place.

Video quality looks good, audio quality good and Amanda speaks well, only thing that is a bit distracting is the jump cut.
Maybe you want to cut away to a short graphic (perhaps a table giving the topics she listed) before she says “…and other fun topics” then cut back to her when she starts saying “make sure you follow and subscribe…”

Very short fade transitions can work well in such circumstances. Because she’s holding a relatively consistent position, a 5-10 frame fade on 30fps is quite smooth but not particularely distracting. I dislike jumpcuts myself and I think they’re a bit old hat now tbh.